In conventional X-ray apparatus the X-ray tube is supplied with high voltage from a power supply through high voltage cables. Except in the special case of low power dental equipment, the high voltage cables must extend many feet from a massive remote high voltage power supply to an arm of the frame supporting the X-ray tube and its receptor, and require thick, high voltage insulation. At least two thick cables are required, each having a substantial capacitance to ground which introduces a slow voltage rise time causing a delay in the application of high voltage to the X-ray tube, and usually a delay in the turn off of X-ray exposure. In addition to being bulky and expensive, the cables are prone to fail in operation particularly when the X-ray tube ionizes near the end of its life.
In conventional metal center X-ray tubes the cathode is at a high negative potential and the envelope of the tube, its rotating anode and anode drive rotor are at a high positive potential. The tube therefor is customarily enclosed in a metal housing additional to its vacuum envelope to shield the high voltage and non-useful radiation from operator and patient. Operation of an X-ray tube also generates such high heat as to limit the length and intensity of X-ray exposure due to thermal limitations of the anode material used, tungsten for example.
Accordingly it is the object of the present invention to provide an X-ray tube and power supply which eliminates the additional housing for the tube envelope, improves the heat dissipation, and eliminates the expense and bulk of high voltage cables and cable connectors, remote power supplies, and the need for heavy power transformers in the supporting arm for the tube.